Heat exchanger

Abstract: A heat exchanger includes upper and lower tanks (2, 3), a plurality of parallel heat transfer tubes (8) fluidly interconnected between the upper and lower tanks (2, 3), a plurality of reinforcing members connecting an upper wall (2a, 3a) and a lower wall (2b, 3b) of the upper and lower tanks (2, 3), and a communication path (9) associated with each reinforcing member. The reinforcing members increase the strength of the tank walls against deformation due to the high pressure working fluid without increasing the thickness of the walls or increasing the spacing between the tubes (8). The communication path (9) ensures efficient flow of a heat medium in the tanks (2, 3).

Description: The present invention relates to a heat exchanger suitable for use in an air conditioning system for vehicles, and more particularly to an improved heat exchanger having a pair of tanks and a plurality of heat transfer tubes interconnected therebetween. Figures 4 to 6 depict a conventional heat exchanger used in an air conditioning system, for example, an evaporator or a condenser. In Figures 4 and 5, a heat exchanger 101 includes an upper tank 102 and a lower tank 103. Upper tank 102 includes an upper wall 102a and a lower wall 102b. Lower tank 103 includes an upper wall 103a and a lower wall 103b. A plurality of heat transfer tubes 104 are fluidly interconnected between lower wall 102b of upper tank 102 and upper wall 103a of lower tank 103. Inlet pipe 105 and outlet pipe 106 are connected to upper tank 102. A heat medium, for example, refrigerant, introduced into inlet pipe 105 flows in heat exchanger 101 from inlet pipe 105 to outlet pipe 106, for example, as shown in Figure 7. When the heat medium flows through heat transfer tubes 104, heat exchange between the heat medium and air flow 107 passing through the heat transfer tubes 104 is performed. In such a conventional heat exchanger, however, because each tank 102, 103 is formed from a thin and flat plate (for example, aluminum plate or aluminum alloy plate), the tank walls may become deformed, as shown by the dashed lines in Figures 4-6, when the pressure in the tanks exceeds a certain level. Upper wall 102a of upper tank 102 and lower wall 103b of lower tank 103 are particularly likely to be deformed. In addressing this problem, two alternative tank constructions have been proposed. The first employs relatively thicker plates, while in the second, partitions are used to connect the upper and lower walls. The former construction increases the weight and cost of the heat exchanger. The latter construction requires a complicated mold for forming a tank, and also increases the cost of the heat exchanger. Further, if too many partitions are disposed in the tank, the heat medium encounters higher fluid resistance. This reduces the efficiency of the heat exchanger. It would be desirable to provide a heat exchanger with tanks having a sufficiently high degree of internal pressure resistance without using a thick plate material, and to manufacture inexpensively a compact, light-weight and efficient heat exchanger. GB-A-194734 discloses a heat exchanger including an upper tank, a lower tank spaced from the upper tank; a plurality of parallel heat transfer tubes fluidly interconnecting the upper and lower tanks; means for reinforcing at least one of the upper and lower tanks by connecting an upper wall and a lower wall thereof; and a communication path associated with each of the reinforcing means, the communication paths providing fluid communication between the interior of the heat transfer tubes and the interior of the tank(s); wherein the reinforcing means comprises a tip portion of each of the heat transfer tubes, the tip portion extending into the interior of the tank through one of the upper and lower walls and connected to the wall opposite to the wall through which the tip portion extends; and the communication paths comprising openings in portions of the heat transfer tubes positioned in the interior of the tank(s), and, according to the present invention, such a heat exchanger is characterised in that a stepped portion is formed on each of the heat transfer tubes, the stepped portion abuttingly engaging an outer surface of the wall through which the tip portion extends. In the new heat exchanger, the reinforcing means increases the internal resistance of tank walls against deformation due to the pressure of the working fluid. The reinforcing means increase the strength of tank walls without increasing the thickness thereof and increasing the pitch of the arrangement of the heat transfer tubes. The communication paths associated with the reinforcing means maintain efficient flow of the heat medium to, from and within the tank. As a result, a compact, light-weight and strong heat exchanger with high efficiency can be inexpensively manufactured. In the accompanying drawings: Figure 1 is a diagrammatic perspective view of a heat exchanger according to a preferred embodiment. Figure 2 is a partial vertical sectional view of a heat exchanger according to Figure 1; Figure 3 is a partial vertical sectional view of the heat exchanger depicted in Figure 2, showing a preferred manufacturing method for the heat exchanger. Figure 4 is an elevational view of a conventional heat exchanger; Figure 5 is a side view of the heat exchanger depicted in Figure 4. Figure 6 is an enlarged partial vertical sectional view of the heat exchanger depicted in Figure 4; and, Figure 7 is a schematic perspective view of a conventional heat exchanger, showing an example of a heat medium flow. Referring to Figure 1, a heat exchanger 1 is provided according to a preferred embodiment. Heat exchanger 1 includes an upper tank 2 and a lower tank 3. The inside of upper tank 2 is divided into two chambers 4a and 4b by a partition 5. Inlet pipe 6 and outlet pipe 7 are connected to upper tank 2. A plurality of heat transfer tubes 8 (for example, refrigerant tubes) are fluidly interconnected between tanks 2 and 3. Heat transfer tubes 8 are arranged in the longitudinal and transverse directions of heat exchanger 1. Each tube 8 has a circular cross section. Upper and lower tanks 2 and 3 and heat transfer tubes 8 are preferably fabricated from an aluminium or an aluminium alloy. With reference to Figure 2, upper tank 2 comprises an upper wall 2a and a lower wall 2b. Lower tank 3 comprises an upper wall 3a and a lower wall 3b. Heat transfer tubes 17 (corresponding to the tubes 8 in Figure 1) extend through holes defined on lower wall 2b of upper tank 2 and holes defined on upper wall 3a of lower tank 3 into the interior of upper and lower tanks 2 and 3. The tips 17b of each heat transfer tube 17 are brought into contact with the inner surface of upper wall 2a of upper tank 2 and the inner surface of lower wall 3b of lower tank 3, respectively. Tips 17b are preferably connected to walls 2a and 3b by brazing. The periphery of each heat transfer tube 17 is preferably fixed to the inner edges of the holes by brazing. Openings 18 are formed in each heat transfer tube 17 at locations within the interior of upper and lower tanks 2 and 3. Although openings 18 are shown as being formed near upper wall 2a or lower wall 3b, they may be formed anywhere along the portions of tubes 17 disposed within tanks 2,3. Openings 18 are preferably formed as U-shaped slots on each end portion 17b. Each opening 18 allows the interior of each heat transfer tube 17 to communicate with the interior of upper tank 2 or lower tank 3. As shown in Figure 2, a stepped portion 16 is formed on each heat transfer tube 17 at each end portion 17b thereof. Stepped portion 16 abuts the outer surface of lower wall 2b of upper tank 2 or upper wall 3a of lower tank 3. As shown in Figure 3, if there is a dimensional inaccuracy in the longitudinal direction of heat transfer tubes 17, a molten brazing material 19 may be pooled on the stepped portion 16 so that heat transfer tube 17 can be surely brazed. The above described structure for reinforcing tanks 2 and 3 can be achieved without changing the pitch of the arrangement of heat transfer tubes 8,17. Moreover, an efficient flow of working fluid from the interior of upper tank 2 or lower tank 3 is ensured by each communication path 18. Consequently, an efficient, durable and inexpensive heat exchanger is obtained. Although the reinforcing and communication structure is formed in both tanks 2 and 3 in the preferred embodiment, the structure may alternatively be applied to only one of the upper and lower tanks 2 and 3.

Claims: A heat exchanger including an upper tank (2), a lower tank (3) spaced from the upper tank; a plurality of parallel heat transfer tubes (8,17) fluidly interconnecting the upper and lower tanks; means (17b) for reinforcing at least one of the upper and lower tanks by connecting an upper wall and a lower wall (2a,2b or 3a,3b) thereof; and a communication path (18) associated with each of the reinforcing means, the communication paths providing fluid communication between the interior of the heat transfer tubes and the interior of the tank(s); wherein the reinforcing means comprises a tip portion (17b) of each of the heat transfer tubes (17), the tip portion extending into the interior of the tank through one of the upper and lower walls (2b,3a) and connected to the wall (2a,3b) opposite to the wall through which the tip portion extends; and the communication paths comprising openings (18) in portions of the heat transfer tubes positioned in the interior of the tank(s); characterised in that a stepped portion (16) is formed on each of the heat transfer tubes (17) the stepped portion abuttingly engaging an outer surface of the wall (2b,3a) through which the tip portion extends. A heat exchanger according to claim 1, wherein the opening (18) is formed at a position near to the opposite wall (2a,3b). A heat exchanger according to claim 1 or claim 2, wherein each of the heat transfer tubes (17) is brazed to the upper and lower walls of at least one of the upper and lower tanks (2,3).

Inventors: AOKI HISAO, CHIBA TOMOHIRO, OIKAWA REI, AOKI, HISAO, CHIBA, TOMOHIRO, OIKAWA, REI
Applicants: SANDEN CORP, SANDEN CORPORATION
Application year: 1994
Main classification: F28D1
IPC codes: F28F9, F28D1